This application relates to the field of testing of sheet materials, and in particular testing of thin glass sheets, such as glass sheets for use in computer flat panel displays, or for semiconductor wafers.
Glass sheets or panels are conventionally maintained, after fabrication of the glass sheets, and before assembly into products, such as flat panel displays, in cassettes. Similarly, semiconductor wafers are placed in cassettes. Cassettes are essentially boxes sized to accommodate sheets or cassettes of a selected size. In one existing design of cassettes, there are provided projecting inward from the sides of the cassette panel supports. A defined distance separates the panel supports. The defined distance is selected to permit an end effector of a robot to pass between the panel supports, so as to remove or insert the panel in the cassette.
After fabrication, and after various steps during processing, panels, semiconductor wafers, and other materials in sheet form, are tested for a variety of physical, electrical, mechanical and chemical properties. Typically, upon fabrication, the panels or wafers are placed in the cassette by a robot with an end effector that engages the panel or wafer in such a manner as to minimize damage. When it is desired to test the panel or wafer, an end effector of a robot is inserted into the cassette, engages the panel or wafer, and transports the panel or wafer from the cassette to a testing device. The robot then places the panel or wafer on suitable supports on the testing device. A handler in the testing device moves the panel or wafer relative to test heads that carry out various tests on the panel or wafer. Upon completion of testing, the robot again engages the panel or wafer and removes the panel or wafer from the test equipment and returns it to the cassette.
This presents several difficulties. Testing time includes time to remove the panel from the cassette and transport it to the test device, and the time required to remove the panel from the test device and return it to the cassette. Each time the panel or wafer is engaged or disengaged by handling equipment, such as the robot end effector or the handler of the test device, there is a risk of damage. The time required to position the sample or sheet before measurement or testing and replace the sample after measurement or testing is increased by the need to have several devices successively engage and release the wafer or panel.
It is an object of the invention to provide a method and apparatus for testing of physical, chemical, electrical and mechanical properties of material in sheet form, such as panels and wafers, that reduces the process time associated with testing the material.
It is a further object of the invention to provide a method and apparatus for testing of material in sheet form that reduces the risk of damage associated with testing of the material.
It is an advantage of the invention that the foregoing objects are achieved.
Additional objects and advantages of the invention will become evident from a review of the detailed description which follows.
An apparatus for testing of material in sheet form includes a cassette adapted to store one or more sheets of material and one or more sensors rigidly mounted with respect to the cassette.
The sensors may be mounted adjacent a test location exterior to the cassette. The cassette and the sensors may be so configured and positioned that a suitable end effector may move sheets of material between storage locations in the cassette and test locations adjacent the sensors.
A method for testing sheet material includes the steps of placing the sheet material in a cassette, and conducting tests employing one or more sensors rigidly mounted with respect to the cassette. The method may include employing an end effector to remove the sheet from the cassette, to position the sheet stepwise in several positions relative to the sensors, and to replace the sheet in the cassette upon completion of testing.
An apparatus for testing of material in sheet form includes sensors that can be positioned adjacent to a surface of material in sheet form located in a cassette and supports positioned to reduce sag of the material.
A method for testing sheet material includes the steps of placing the sheet material in a cassette, and testing the sheet material while in the cassette.
A cassette according to the invention includes shelves having defined therein test heads for testing properties of material in sheet form.